The present invention relates to a four-element catalyst employed for various chemical reactions, especially for an electrocatalyst for anode of a fuel cell.
A carbon catalyst supported with element platinum as electrode material has been heretofore widely employed as an electrocatalyst for anode of a fuel cell.
However, as an anode gas of the fuel cell, such a reformed gas as a liquefied natural gas (LNG) is employed in which a carbon monoxide gas (CO) is contained.
Platinum is likely to adsorb the carbon monoxide gas which results in considerable poisoning at a low temperature.
In order to avoid the poisoning, the fuel cell is operated at a temperature more than 190.degree. C. to reduce the influence of the carbon monoxide.
In the fuel cell having the element platinum catalyst, its reaction is conducted at a temperature more than that required inevitably employing disadvantageous various operation conditions encountered in higher temperature reactions. Further, the poisoning cannot be completely avoided even under said conditions resulting in the advance of polarization to invite the lowering of electrode performance.
A fuel cell employing a solid polymer electrolyte (SPE) possesses a problem that the poisoning of the element platinum with the carbon monoxide is hardly avoided because of a lower operation temperature due to the weakness of the electrolyte against heat.
In order to overcome these problems, a catalyst comprising a platinum-palladium or a platinum-ruthenium alloy is already known.
However, the improvement attained by employing these catalysts is unsatisfactory and a further improvement is desirably requested.